“Black powder” refers to blackish material such as solids or solid deposits that collects in gas pipelines. In some implementations, the black powder has a wet, tar-like appearance, or may appear as a dry, fine powder material composed of iron hydroxide, iron carbonate, iron sulfide, or other components and may be mixed with various contaminants such as salts, sand, and liquid hydrocarbons.
Deposition or formation of black powder can occur if there are solids in the pipeline fluid and the velocity of the gas flow is not high enough to drag the particles along by viscous flow forces. Sediment deposits can lead to blockage of the line, especially during pigging, while flowing powder can damage compressors, plug filters, and damage user equipment. Black powder also represents a threat to natural gas's reputation as a clean fuel.